Novel extraction agents and novel propane diamides

ABSTRACT

The invention relates to novel extracting agents and novel propane diamides, their use for the recovery of actinides and/or lanthanides and their preparation process. These extracting agents are constituted by propane diamides of formula: ##STR1## For example, the extracting agent can be 2-hexyl-N,N&#39;-dimethyl-N,N&#39;-dibutyl-propane diamide or 2-ethoxyethyl-N,N&#39;-dimethyl-N,N&#39;-dibutyl-propane diamide. They are more particularly used for the recovery of actinides and/or lanthanides present in the trivalent state in an acid aqueous solution, particularly in a nitric solution.

BACKGROUND OF THE INVENTION

The present invention relates to the extraction of metals by means ofextraction agents constituted by propane diamides and it moreparticularly applies to the recovery of actinides and/or lanthanidespresent in the trivalent state in an acid aqueous solution, particularlyin a nitric solution.

In irradiated nuclear fuel reprocessing installations, during the firsturanium and plutonium extraction stage, aqueous solutions of fissionproducts are obtained, which contain relatively large quantities oftrivalent ions of lanthanides and actinides. The effluents from theseinstallations also contain the same ions.

In view of the relatively long half-life of trivalent actinide elements,it is of great interest to separate them from nitric aqueous solutionsin order to obviate the manipulation of effluents or waste having a highα activity. Hitherto, this separation has been carried out by solventextraction using as extractants neutral or acid organophosphoruscompounds, such as tributyl phosphate or di-2-ethylhexylphosphoric acid.However, the use of such extractants has not proved to be particularlyadvantageous, because their extraction yield with respect to trivalentions is low and their industrial use leads to numerous problems due tothe necessity of using large amounts of salifying agents, whichincreases the volume of the waste and the processing costs.

Consideration has also been given to the use for said separation ofother neutral or bidentate organophosphorus compounds, such asdiphosphonates and carbamyl phosphonates, together with amides, such asis described in J. Inorg. Nucl. Chem. 25, 1963, pp 883-892; J. Inorg.Nucl. Chem. 26, 1964, pp 1991-2003; and Separation Science andTechnology, 15, 4, pp 825-844, 1980.

However, the results obtained are not satisfactory, particularly in thecase of diamides such as tetrabutyl malonamide, because the extractionyields are very low.

However, research has been carried out on other diamides and it has beenfound that diamides of formula: ##STR2## in which R is an alkyl radicalwith between 2 and 10 carbon atoms made it possible to obtainsatisfactory results, as described in French Pat. No. 2 537 326, filedon 1.12.1982 by the Commissariat a l'Energie Atomique. However, suchdiamides suffer from the disadvantage of mostly being in solid form,which leads to problems in connection with the use thereof.

SUMMARY OF THE INVENTION

The present invention specifically relates to novel extraction agentsmore particularly usable for the recovery of actinides and/orlanthanides by extraction in an organic solvent containing at least onepropane diamide, which obviates the aforementioned disadvantage andwhich also makes it possible to obtain improved extraction coefficients.

These novel extraction agents are constituted by a propane diamide offormula: ##STR3## in which R¹ and R², which can be the same ordifferent, represent a straight or branched alkyl radical having 1 to 15carbon atoms or a radical of formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m --O--R.sup.4

in which R⁴ is an alkyl radical with 1 to 6 carbon atoms, n is equal to0 or is an integer ranging between 1 and 6, Z is a single bond or anoxygen atom and m is an integer ranging between 1 and 6, provided that Zis a single bond when n is equal to 0 and R³ represents a hydrogen atom,an alkyl radical with 1 to 15 carbon atoms, a radical of formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m --O--R.sup.4

in which n, m, Z and R⁴ have the meanings given hereinbefore, or aradical of formula: ##STR4## in which R¹ and R² have the meanings givenhereinbefore, provided that R³ does not represent a hydrogen atom whenR¹ and R² both represent an alkyl radical.

These propane diamides can be used for recovering metals from generallyacid aqueous solutions. These metals can belong to the group oftransition metals, such as iron and zirconium, to the group oflanthanides or to the group of actinides.

The use for the extraction of metals of propane diamides in accordancewith the above formula makes it possible to obtain improved extractioncoefficients compared with those obtained with the prior art propanediamides, which are only tetrasubstituted by alkyl radicals.

Preferably, according to the invention, radical R¹ is a methyl radical.Preferably, one of the radicals R² and R³ is a radical in accordancewith formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m --O--R.sup.4

in which m, n, Z and R⁴ have the meanings given hereinbefore. Thus, thepresence of a substituent having at least one other oxide function makesit possible to obtain even better actinide and lanthanide extractioncoefficients than those obtained with propane diamides pentasubstitutedby alkyl radicals.

According to a preferred embodiment of the invention, the propanediamide is in accordance with formula (I), in which R¹ is the methylradical, R² an alkyl radical and R³ the radical of formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m --O--R.sup.4

in which n, m, Z and R⁴ have the meanings given hereinbefore.

In this preferred embodiment, the substituents which can be used cancomprise a single ether oxide function. In this case, n is equal to 0, Zis a single bond and preferably m is equal to 1, 2 or 3, whilst R⁴ is analkyl radical with 2 to 6 carbon atoms.

The substituents which can be used can also have two ether oxidefunctions. In this case, it is in particular possible to usesubstituents in which n=2, Z represents an oxygen atom, m is equal to 2and R⁴ is an alkyl radical with 2 to 6 carbon atoms.

The invention also relates to novel propane diamides according toformula: ##STR5## in which R¹ and R², which can be the same ordifferent, represent a straight or branched alkyl radical with 1 to 15carbon atoms or a radical of formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m --O--R.sup.4

in which R⁴ is an alkyl radical with 1 to 6 carbon atoms, n is equal to0, or is an integer ranging between 1 and 6, Z is a single bond or anoxygen atom and m is an integer ranging between 1 and 6, provided that Zis a single bond when n is equal to 0 and R³ represents a hydrogen atom,an alkyl radical with 1 to 15 carbon atoms, or a radical of formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m --O--R.sup.4

in which n, m, Z and R⁴ have the meanings given hereinbefore, providedthat R³ does not represent a hydrogen atom or an alkyl radical having 1to 3 carbon atoms when R¹ and R² both represent an alkyl radical.

Preferably, at least one of the radicals R¹, R² and R³ complies with theformula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m OR.sup.4

in which n, m, Z and R⁴ have the meanings given hereinbefore.

When R³ represents a hydrogen atom, tetrasubstituted propane diamidesare obtained. Examples of such propane diamides areN,N'-dimethyl-N,N'-dioctoxyethyl-propane diamide of formula: ##STR6##when R³ differs from a hydrogen atom, pentasubstituted propane diamidesare obtained. Examples of such propane diamides are propane diamides offormula (I), in which R¹ is the methyl radical, R² the butyl radical andR³ a radical chosen from among the ethoxyethyl, butoxyethyl, hexoxyethyland hexoxyethoxyethyl radicals and the propane diamide for formula (I)in which R¹ is the methyl radical, R² the octyl radical and R³ thehexoxyethyl radical.

These propane diamides are particularly interesting, because thepresence of an ether oxide function on one of the substituents makes itpossible to obtain improved properties for the extraction of actinidesand lanthanides.

According to the invention, the propane diamide can also be a propanediamide pentasubstituted by alkyl radicals. Examples of such compoundsare propane diamides in accordance with formula (I), in which R¹ is themethyl radical, R² the butyl radical and R³ the butyl or hexyl radical.

The propane diamides according to the invention can be in the form of amixture of isomers or in the form of isomers. Furthermore, it is pointedout that the formulas given herein can either represent a mixture ofisomers or one of the isomers.

The novel extraction agents based on pentasubstituted propane diamidesaccording to the invention can be prepared by a four stage process onthe basis of an alkyl malonate. In the first stage, to the alkylmalonate is fixed the radical of formula R³ by the reaction of the alkylmalonate with a halide of formula R³ X in the presence of sodium, whichcorresponds to the following reaction diagram: ##STR7## in which R⁵represents an alkyl radical.

In the second stage, hydrolysis takes place of the branched malonateobtained in the first stage by means of soda or potash, whichcorresponds to the following reaction diagram: ##STR8## The thusobtained substituted malonic acid is then transformed into malonylchloride by reaction thereof with SOCl₂, which corresponds to thefollowing reaction diagram: ##STR9## After these reactions, there is anamination of the malonyl chloride by reacting the latter with thecorresponding amine of formula ##STR10## which corresponds to thefollowing diagram: ##STR11## The halides of formula R³ X used when R³contains an ether oxide group can be prepared by conventional processes,e.g. by the process described by F. C. Cooper and M. W. Partridge in J.Chem. Soc., 1950, p 459. However, this procedure for preparingpentasubstituted propane diamides suffer from the disadvantage ofrequiring several stages.

The present invention also proposes a process for the preparation ofpentasubstituted propane diamides making it possible to obviate thisdisadvantage. This process for the preparation of a pentasubstitutedpropane diamide according to formula: ##STR12## in which R¹, R² and R³have the meanings given hereinbefore, consists of reacting atetrasubstituted propane diamide of formula: ##STR13## in which R¹ andR² have the meanings given hereinbefore with a halide of formula R³ X,in which X represents a halogen atom, in the presence of metallationagents, e.g. n-butyl lithium or t-butyl lithium.

In this process, the halides of formula R³ X are preferably bromides oriodides and they can be prepared, when R³ contains an ether group, byusing the process described by F. C. Cooper and M. W. Partridge in J.Chem. Soc., 1950, p 459.

In the process according to the invention, there is firstly ametallation reaction of the tetrasubstituted propane diamide, e.g. by nor t-butyl lithium in accordance with the following reaction diagram:##STR14## and then the halide of formula R³ X is condensed on theproduct formed during the metallation reaction in accordance with thefollowing reaction diagram: ##STR15## The tetrasubstituted propanediamides used as the starting product in the process according to theinvention can be prepared by the amination of the malonyl chloride bymeans of corresponding amines of formula ##STR16## using the reactiondescribed hereinbefore in the case of substituted malonyl chlorides.This reaction is generally performed in the presence of a catalyst, suchas triethyl amine. This procedure for the preparation oftetrasubstituted propane diamides still suffers from the disadvantage ofleading to very low yields, when the hydrocarbon chains R¹ and/or R² ofthe amine have more than four carbon atoms.

Furthermore, the present invention proposes another process for thepreparation of tetrasubstituted propane diamides making it possible toobtain good yields, even when the radicals R¹ and/or R² of the aminehave more than 4 carbon atoms.

According to the invention, preparation takes place of tetrasubstitutedpropane diamides of formula: ##STR17## in which R¹ and R² have themeanings given hereinbefore, by reacting an alkyl malonate of formula:##STR18## in which R⁵ represents an alkyl radical, with thecorresponding amine of formula ##STR19## in the presence of a catalyst.

This corresponds to the following reaction diagram: ##STR20## Generally,the alkyl malonate is ethyl malonate and the reaction takes place in thepresence of a catalyst such as hydroxypyridine, operating at atemperature above ambient temperature and e.g. at 140° to 170° C.

The starting amines used for the preparation of the tetrasubstitutedpropane diamides and pentasubstituted propane diamides can be preparedby conventional processes, particularly that described by J. L. Nelsonand RC. Sentz in J. Amer. Chem. Soc. vol. 74, p 1704, 1952.

The inventive process for the preparation of pentasubsituted propanediamides thus has the advantage of making it possible to obtain suchproducts in two stages from commercial products, such as ethyl malonateand the halide of formula R³ X. Moreover, the process according to theinvention is advantageous because it places the critical branchingstage, i.e. the introduction of radical R³, last, whereas it isperformed first in the four stage synthesis process.

When the extraction agent corresponds to formula: ##STR21## in which R¹and R² can be the same or different and represent a straight or branchedalkyl radical with 1 to 15 carbon atoms or a radical of formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m --O--R.sup.4

in which R⁴ is an alkyl radical with 1 to 6 carbon atoms, n is equal to0 or is an integer ranging between 1 and 6, Z is a single bond or anoxygen atom and m is an integer ranging between 1 and 6, provided that Zis a single bond when n=0, the process consists of reacting atetrasubstituted propane diamide of formula: ##STR22## in which R¹ andR² have the meanings given hereinbefore with a methoxyalkyl halide offormula XCH₂ OR, which X represents a halogen atom and R an alkylradical with 1 to 8 carbon atoms, e.g. a methoxymethyl halide of formulaXCH₂ --OCH₃, in the presence of a metallation agent, such as n-butyllithium or t-butyl lithium.

Under these conditions two tetrasubstituted propane diamide moleculesreact with a methoxyalkyl halide in which the alkyl contains 1 to 8carbon atoms, e.g. a methoxymethyl halide, generally bromide, forforming the pentasubstituted propane diamide according to formula (II).

When use is made of the processes described hereinbefore, the productobtained is constituted by a mixture of isomers.

According to the invention, the extraction agent used can be one ofthree isomers or a mixture thereof and it is pointed out that theformulas given herein can either represent one of these isomers or themixture of isomers obtained by the processes described hereinbefore.

The invention more particularly applies to the recovery of actinidesand/or lanthanides present in the trivalent state in an acid aqueoussolution.

The invention also relates to a process for the recovery of actinidesand/or lanthanides present in the trivalent state in an acid aqueoussolution, which consists of contacting said aqueous solution with anorganic phase comprising at least one extraction agent chosen from amongthe extraction agents based on propane diamides according to formula(I).

According to the invention, the organic phase used for extractionpurposes generally comprises a diluent and the propane diamideconcentration of the organic phase is preferably 0.1 to 1.5 mol.l⁻¹.

Thus, the extraction rate generally increases with the propane diamideconcentration of the organic phase. However, to maintain the viscosityand density of the organic phase in an appropriate range, use isgenerally made of propane diamide contents not exceeding 1.5 mol.l⁻¹.

The diluents which can be used are inert organic diluents preferablyhaving a not very high dielectric constant. Examples of such diluentsare benzene, xylene, mesitylene, t-butyl benzene, dodecane and mixturesthereof.

Generally the diluent used is a mixture of decanol and a compound chosenfrom among benzene, xylene, mesitylene, t-butyl benzene and dodecane,because the presence of decanol makes it possible to avoid the formationof a third phase for low concentrations of lanthanides or actinidesextracted in the organic phase. However, so as not to excessively reducethe extraction yield, the organic phase generally comprises at the most20% by volume of decanol.

The process according to the invention can be used for recoveringactinides and lanthanides from different aqueous solutions, but inparticular nitric solutions.

The process according to the invention can be performed in anyconventional extraction apparatus, such as groups of mixer-settlermeans, pulsed columns, centrifugal extractors, etc. Generally, workingtakes place at ambient temperature and pressure with aqueousphase:organic phase volume ratios between 10:1 and 1:10.

The actinides (III) and lanthanides (III) extracted in the organic phasecan then be recovered with very good yields by reextraction in water.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail hereinafter relative tonon-limitative embodiments and the attached drawings, wherein show:

FIGS. 1 and 2. Graphs showing the variations of the distributioncoefficients D_(Am) of americium and D_(Eu) of europium, as a functionof the nitric acid concentration of the aqueous solution to be treated,when using as the organic extractant2-hexyl-N,N'-dimethyl-N,N'-dibutyl-propane diamide (FIG. 1) and2-ethoxyethyl-N,N'-dimethyl-N,N'-dibutyl-propane diamide (FIG. 2), atconcentrations of 0.5 mol.l⁻¹ in a diluent of 90% t-butyl benzene and10% decanol.

FIGS. 3 and 4. Graphs showing the variations of the distributioncoefficients D_(Am) of americium and D_(Eu) of europium as a function ofthe diamide concentration of the organic phase when using as the diamide2-hexyl-N,N'-dimethyl-N,N'-dibutyl-propane diamide (FIG. 3) and2-ethoxyethyl-N,N'-dimethyl-N,N'-dibutyl-propane diamide (FIG. 4) and adiluent of 90% t-butyl benzene and 10% decanol, the aqueous phase being5N nitric acid.

FIG. 5. A diagram showing the variations of the distributioncoefficients D_(Am) and D_(Eu) as a function of the decanolconcentration of the diluent of the organic phase.

FIG. 6. A diagram showing the variations of the distributioncoefficients D_(Am) and D_(Eu), as a function of the nitric acidconcentrations of the aqueous solution to be treated, when using as theextractant N,N'-dimethyl-N,N'-diethoxyoctyl propane diamide at aconcentration of 0.5 mol.l⁻¹ in t-butyl benzene.

FIG. 7. A graph showing the variations of the distribution coefficientsD_(Am) and D_(Eu) as a function of the nitric acid concentration of theaqueous solution to be treated, when using as the extractant(2-(3,6-OD)DBDMPDA.

FIG. 8. A graph showing the variations of the distribution coefficientsD_(U), D_(Pu), D_(Zr), D_(FE) and D_(Nb) as a function of the nitricacid concentration of the aqueous solution, when using as the extractantthe propane diamide according to the invention constituted by compound11.

DETAILED DESCRIPTION OF THE INVENTION

Examples 1 and 2 illustrate the preparation of tetrasubstituted propanediamides.

Examples 3 to 7 illustrate the preparation of pentasubstituted propanediamides using the process according to the invention and the novelcompounds obtained by this process.

Examples 8 to 17 illustrate the use of the propane diamides according tothe invention for the extraction of actinides and lanthanides.

EXAMPLE 1

Preparation of N,N'-dimethyl-N,N'-dioctyl-propane diamide (compound 1)of formula: ##STR23## 0.30 mol of ethyl malonate, 0.225 ml of2-hydroxypyridine and 1.44 mol of methyl-N-octyl-amine are placed in aone liter reactor, scavenged by a nitrogen stream and equipped with aVigreux column, a condenser and a receiving flask. Progressive heatingtakes place and at 175° C. ethyl alcohol is separated on the oil bath.Heating is continued until the end of alcohol separation (185° C. on theoil bath). Cooling takes place, followed by taking up with 300 ml ofchloroform, washing with water to eliminate the pyridine, settling,drying, removing the solvent and distillation. After distilling thestarting amine (72°-75° C./15 mm Hg) (2025 Pa), the sought productdistills at 185°-190° C. under 0.1 mm Hg (13.5 Pa). 55 g of a yellowliquid are recovered with a yield of 52%. The product crystallizes inhexane at +5° C. (m.p.=41° C.) it being characterized by the nuclearmagnetic resonance of the proton and by potentiometry.

EXAMPLE 2

In the same way as in example 1 are prepared the tetrasubstitutedpropane diamides (compounds 2 to 5 of the following table) using ethylmalonate and amines corresponding to formula ##STR24## The yieldsobtained and the boiling points of the tetrasubstituted propane diamidesare also given in table 1. It also provides the results obtained withthe tetrasubstituted propane diamide of example 1 (compound 1).

                  TABLE 1                                                         ______________________________________                                         ##STR25##                                                                    Compound No.                                                                            R.sup.1                                                                              R.sup.2    Yield                                                                              b.p.                                         ______________________________________                                        1(DIAM 8) CH.sub.3                                                                             C.sub.8 H.sub.17                                                                         52%  185-190° C./1 mm                                                       (135 Pa)                                     2(DIAM 6) CH.sub.3                                                                             C.sub.6 H.sub.13                                                                         30%  170-175° C./0.5 mm                                                     (67.5 Pa)                                    3(DIAM 4,8)                                                                             C.sub.4 H.sub.9                                                                      C.sub.8 H.sub.17                                                                         25%  --                                           4(DIAM 4,4)                                                                             C.sub.4 H.sub.9                                                                      C.sub.4 H.sub.9                                                                          47%  172-177° C./1 mm                                                       (135 Pa)                                     5(DIAM 802)                                                                             CH.sub.3                                                                             C.sub.2 H.sub.4 OC.sub.8 H.sub.17                                                        50%  --                                           ______________________________________                                    

EXAMPLE 3

Preparation of 2-hexyl-N,N'-dimethyl-N,N'-dibutyl-propane diamide(2-HDBDMPDA) (compound 6)

(a) preparation of N,N'-dimethyl-N,N'-dibutyl-propane diamide offormula: ##STR26## 2 mol of N-methyl-N-butyl amine in 600 ml ofmethylene chloride are introduced into a two liter reactor scavenged bya nitrogen stream. 2 mol of triethyl amine are added to trap thehydrochloric acid. Pouring then takes place at 5° C. of a malonylchloride solution prepared from 1 mol of malonyl chloride in 300 ml ofmethylene chloride and following the addition of the said solution,refluxing of the methylene chloride takes place for 4 hours. Cooling isfollowed by filtration, abundant washing with water to eliminate thetriethylamine hydrochloride, drying the organic phase, expelling thesolvent and distillation. In this way 97 g of a liquid is recovered,which distills at 140°-144° C. under 0.3 mm of mercury (40.5 Pa), whichcorresponds to a 40% yield. This product crystallizes in hexane at 5° C.(m.p. 51.5° C.). This product is characterized by nuclear magneticresonance of the proton and by potentiometric dosing and it isestablished that it corresponds to the above formula.

(b) Preparation of 2-hexyl-N-N'-dimethyl-N,N'-dibutyl-propane diamide offormula: ##STR27## 0.1 mol of N,N'-dimethyl-N,N'-dibutyl-propane diamidedissolved in 400 ml of tetrahydrofuran are introduced into a one literreactor, scavenged by a nitrogen stream. Cooling takes place to -50° C.using an acetone bath and solid carbon dioxide and pouring takes placeof a solution of n-butyl lithium prepared from 0.1 mol of n-butyllithium in 100 ml of anhydrous tetrahydrofuran. Under the sameconditions is poured a solution of hexyl iodide prepared from 0.1 mol ofhexyl iodide and 100 ml of anhydrous tetrahydrofuran. When pouring is atan end, the temperature is allowed to rise to ambient temperature again,followed by refluxing the tetrahydrofuran for three hours. Cooling isallowed to take place, followed by hydrolysis with a water-ethanolmixture. The tetrahydrofuran is expelled and in this way a precipitateis formed. This is taken up with methylene chloride, followed by washingwith water, drying the organic layer, expelling the solvent and thendistillation. The boiling point is 145° to 148° C. under 0.4 mm ofmercury and the product is a yellow liquid. Its characterization bynuclear magnetic resonance of the proton and by potentiometric dosageconfirms that it corresponds to the above formula.

The following were prepared in the same way:2,N,N'-trimethyl-N,N'-dibutyl-propane diamide,2-ethyl-N,N'-dimethyl-N,N'-dibutyl-propane diamide and2,N,N'-trimethyl-N,N'-dioctyl with respectively yields of 66%, 61.5% and65.2% from the N,N'-dimethyl-N,N'-dibutyl-propane diamide obtained inexample 3a) or N,N'-dimethyl-N,N'-dioctyl-propane diamide obtained inexample 1 using as halides methyl iodide or ethyl iodide.

EXAMPLE 4

Preparation of 2-butyl-N,N'-dimethyl-N,N'-dibutyl-propane diamide(compound 7).

As in example 3(a), N,N'-dimethyl-N,N'-dibutyl-propane diamide wasprepared and was then reacted by following the operating procedure ofexample 3(b) with butyl iodide. This gave2-butyl-N,N'-dimethyl-N,N'-dibutyl-propane diamide with a yield of47.6%.

EXAMPLE 5

Preparation of 2-ethoxyethyl-N,N'-dimethyl-N,N'-dibutylpropane diamide(2-(3-OP)DBDMPDA) (compound 8) of formula: ##STR28## 0.1 mol ofN,N'-dimethyl-N,N'-dibutyl-propane diamide obtained in example 3(a)dissolved in 400 ml of anhydrous tetrahydrofuran were introduced into aone liter reactor, scavenged by an argon flow. Cooling took place to-50° C. using an acetone bath and solid carbon dioxide and pouring tookplace of a solution of n-butyl lithium prepared from 0.1 mol of n-butyllithium in 100 ml of anhydrous tetrahydrofuran. Under the sameconditions was prepared a solution of ethoxy-2-ethyl bromide of formulaBrCH₂ --CH₂ --O--C₂ H₅ prepared from 0.1 mol of bromide and 100 ml ofanhydrous tetrahydrofuran. With pouring at an end, the temperature wasallowed to rise to ambient temperature, followed by refluxing thetetrahydrofuran for three hours. This was followed by cooling andhydrolysis with a water-ethanol mixture. The tetrahydrofuran wasexpelled and a precipitate formed, followed by taking up with methylenechloride. This was followed by washing with water, drying the organiclayer, expelling the solvent before performing chromatography on asilica gel column using as the eluent a mixture of ethyl acetate andcyclohexane (80:20 by volume). A yellow liquid was recovered constitutedby 2-ethoxyethyl-N,N'-dimethyl-N,N'-dibutyl-propane diamide. The productwas characterized by mass spectrometry, magnetic resonance of the protonand potentiometry, the eld was 40%.

EXAMPLE 6

In the same way as in example 5, the pentasubstituted propane diamideswere prepared (compounds 9 to 12 of table 2) by reacting theN,N'-dimethyl-N,N'-dibutyl-propane diamide obtained example 3 with thecorresponding bromides in the case of compounds 9 to 11, orN,N'-dimethyl-N,N'-dioctyl-propane diamide obtained in example 1 withthe corresponding alkyl bromide in the case of compound 12.

The yields obtained are also given in table 2, which also gives theresults obtained with the pentasubstituted propane diamide of example 5(compound 8).

In the case of compound 11 of table 2, use was also made of apurification procedure other than silica gel column chromatography. Thispurification treatment was performed in the following way. 200 g ofcrude product was stirred with 2 liters of 1N hydrochloric acid for 24hours, followed by settling. This operation was repeated three times andthe organic part was taken up in 200 ml of methylene chloride, followedby washing with water and flash distillation. This gave a 98% pureproduct with a yield of 40%. This purification procedure was also usedfor the other compounds of table 2.

                  TABLE 2                                                         ______________________________________                                        Com-                                                                          pound R.sup.1                                                                              R.sup.2 R.sup.3           Yield                                  ______________________________________                                        No. 8 CH.sub.3                                                                             C.sub.4 H.sub.9                                                                       C.sub.2 H.sub.4 OC.sub.2 H.sub.5                                                                40%                                    No. 9 CH.sub.3                                                                             C.sub.4 H.sub.9                                                                       C.sub.2 H.sub.4 OC.sub.4 H.sub.9                                                                52.7%                                  No. 10                                                                              CH.sub.3                                                                             C.sub.4 H.sub.9                                                                       C.sub.2 H.sub.4 OC.sub.6 H.sub.13                                                               55.6%                                  No. 11                                                                              CH.sub.3                                                                             C.sub.4 H.sub.9                                                                       C.sub.2 H.sub.4 OC.sub.2 H.sub.4 OC.sub.6 H.sub.13                                              40.5%                                  No. 12                                                                              CH.sub.3                                                                             C.sub.8 H.sub.17                                                                      C.sub.2 H.sub.4 OC.sub.6 H.sub.13                                                               51%                                    No. 14                                                                              CH.sub.3                                                                             C.sub.4 H.sub.9                                                                       C.sub.2 H.sub.4 OC.sub.2 H.sub.4 OC.sub.8 H.sub.17                                              60%                                    No. 15                                                                              CH.sub.3                                                                             C.sub.4 H.sub.9                                                                        ##STR29##        55%                                    ______________________________________                                    

EXAMPLE 7

Preparation of bis-[N,N'-dimethyl-N,N'-dibutyl-propanediamide]-2,2-methylene (compound 13) of formula: ##STR30## 0.1 mol ofN,N'-dimethyl-N,N'-dibutyl-propane diamide obtained in example 3(a) anddissolved in 400 ml of anhydrous tetrahydrofuran (THF) were introducedinto a one liter reactor, scavenged by an argon flow. Cooling took placeto -50° C. using an acetone-solid carbon dioxide bath and pouring tookplace of a solution of n-butyl lithium prepared from 0.1 mol of n-butyllithium in 100 ml of anhydrous THF. Under the same conditions, pouringtook place of a bromo methoxy methane solution prepared from 0.1 mol ofbromide in 100 ml of anhydrous THF. With pouring at an end, thetemperature was allowed to rise to ambient temperature and then the THFwas refluxed for three hours. Cooling was allowed to take place,followed by hydrolysis with a water-ethanol mixture. The THF wasexpelled and the residue taken up with methylene chloride. This wasfollowed by washing with water, drying the organic layer and expellingthe solvent before carrying out silica gel chromatography using as theeluant a mixture of ethyl acetate and cyclohexane (80:20 by volume).15.8 g of a very viscous yellow product were recovered (yield=63.4%).

This product was characterized by mass spectrometry, nuclear magneticresonance of the proton and potentiometry.

EXAMPLE 8

This example illustrates the recovery of americium and europiumrespectively present at concentrations of 10⁻⁴ mol.l⁻¹ for Am (III) and10⁻² mol.l⁻¹ for Eu (III) in nitric aqueous solutions of differentacidities.

In all cases, use was made of an organic phase constituted by propanediamide formed by compound 6 obtained in example 3 (2-HDBDMPDA)dissolved in a mixture of t-butyl benzene and decanol (90% by volumet-butyl benzene and 10% by volume of decanol), the diamide concentrationof the organic phase being 0.5 mol.l⁻¹. In this example, extractiontakes place by contacting under stirring the organic phase and theaqueous phase containing the americium and europium with an organicphase:aqueous phase volume ratio of 1.

Following 4 minutes contacting accompanied by stirring, the phases areallowed to settle and the americium and europium concentrations of theaqueous and organic phases are measured. In this way it is possible todetermine the distribution coefficients of the americium and europiumD_(Am) and D_(Eu) corresponding to the ratio of the concentration of theelement (Am or Eu) in the organic phase to the concentration of the sameelement in the aqueous phase. The results obtained are given in FIG. 1,where curves 1 and 2 respectively illustrate the variations of D_(Am)and D_(Eu) as a function of the nitric acid concentration of the aqueousphase (in mol.l⁻¹).

In FIG. 1, curve 3 (in dotted line form) illustrates the resultsobtained with regards to the americium distribution coefficient, whenextraction is carried out under the same conditions using the prior artN,N'-dimethyl-N,N'-dioctylpropane diamide.

These results show that the distribution coefficients of americium andeuropium increase with the nitric acid concentration of the aqueousphase and they have a maximum for a for a nitric acid concentration ofapproximately 5 mol.l⁻¹. In the case of the prior art propane diamide(curve 3), the americium distribution coefficient has a maximum for anitric acid concentration of 2 mol.l⁻¹, but this maximum is below thatobtained with the diamide according to the invention.

EXAMPLE 9

This example also relates to the extraction of the americium andeuropium respectively present at concentrations of 10⁻⁴ mol.l⁻¹ for Am(III) and 10⁻² mol.l⁻¹ for Eu (III) in the nitric aqueous solutions ofdifferent acidities using propane diamide constituted by compound 8obtained in example 5 (2-(3-OP)DBDMPDA).

In all cases, use is made of an organic phase constituted by the diamideobtained in example 5, i.e.2-ethoxyethyl-N,N'-dimethyl-N,N'-dibutyl-propane diamide(2-(3-OP)DBDMPDA) at a concentration of 0.5 mol.l⁻¹ in an organic phasehaving 90% by volume of t-butyl benzene and 10% by volume of decanol.Extraction of the europium and americium takes place under the sameconditions as in example 8 and after 4 minutes contacting time, theamericium and europium concentrations of the aqueous phase and organicphase are measured. The americium and europium distribution coefficientsare then determined.

The results obtained are given in FIG. 2, where curves 4 and 5respectively illustrate the distribution coefficients D_(Am) and D_(Eu),as a function of the nitric acid concentration of the aqueous phase (inmol.l⁻¹).

In FIG. 2, the dotted line curve 6 relates to the results obtained underthe same conditions for americium with the prior artN,N'-dimethyl-N-N'-dioctyl-propane diamide (DODMPDA). It is possible tosee that the americium and europium distribution coefficient increaseswith the nitric acid concentration of the aqueous phase and that thebest distribution coefficients are obtained for nitric acidconcentrations of 5 to 6 mol.l⁻¹.

When using the prior art propane diamide (curve 6) the maximumextraction coefficient for americium is obtained for nitric acidconcentrations of 2 to 3 mol.l, but this maximum is well below themaximum obtained with the propane diamide according to the invention.

EXAMPLE 10

This example also relates to the recovery of the americium and europiumpresent in the trivalent state in an aqueous nitric phase having a HNO₃concentration of 5 mol.l⁻¹, Am (III) concentration of 10⁻⁴ mol.l⁻¹ and aEu (III) concentration of 10⁻² mol.l⁻¹.

For the extraction, use is made of an organic phase constituted bycompound 6 (2-HDBDMPDA) obtained in example 3 in a mixture of t-butylbenzene and decanol containing 10% by volume of decanol. Extractiontakes place under the same conditions as those of examples 8 and 9,using organic phases having different propane diamide concentrations.The results are given in FIG. 3, which illustrates the distributioncoefficient D_(Am) and D_(Eu) as a function of the diamide concentrationof the organic phase (in mol.l-1). Line 7 relates to americium and line8 to europium.

On the basis of these results, it can be seen that the distributioncoefficient D_(Am) and D_(Eu) increase rapidly with the propane diamideconcentration of the organic phase.

EXAMPLE 11

In this example, extraction takes place of the Am (III) and Eu (III)ions from an aqueous phase identical to that of example 9 using anorganic phase constituted by 2-(3-OP) DBDMPDA, namely compound 8 inexample 5, in a mixture of t-butyl benzene and decanol containing 10% byvolume of decanol. Extraction takes place under the same conditions asin example 9 using different propane diamide concentrations in theorganic phase. The results obtained are given in FIG. 4, which shows thedistribution coefficients D_(Am) and D_(Eu) as a function of the propanediamide concentration of the organic phase.

Curve 9 relates to americium and curve 10 to europium. It can be seenthat the distribution coefficients D_(Am) and D_(Eu) rapidly increasewith the propane diamide concentration of the organic phase.

EXAMPLE 12

This example relates to the recovery of americium (III) and europium(III) from an aqueous solution identical to that of examples 10 and 11.

In this example, use is made of organic phases comprising either 0.5mol.l⁻¹ or 2-HDBDMPDA (compound 6) or 0,.5 mol.l⁻¹ of 2-(3-OP) DBDMPDA(compound 8) in a mixture of t-butyl benzene and decanol with differentt-butyl benzene and decanol ratios. Extraction takes place under thesame conditions as in examples 10 and 11 and the distributioncoefficients of americium and europium are determined after extraction.The results obtained are given in FIG. 5 showing the distributioncoefficients of americium and europium as a function of the decanolvolume percentage in the organic phase.

Curve 11 relates to americium and to the propane diamide of example 5(2-(3-OP)DBDMPDA, curve 12 relates to americium and propane diamide ofexample 3 (2-HDBDMPDA), curve 13 relates to europium and propane diamideof example 5 (2-(3-OP)DBDMPDA) and curve 14 relates to europium andpropane diamide of example 3 (2-HDBDMPDA).

On the basis of these results, it can be seen that the distributioncoefficients decrease when the decanol proportion of the organic phaseincreses.

EXAMPLE 13

This example studies the influence of decanol on the praseodymiumnitrate limiting concentration in the organic phase, which must not beexceeded to avoid the formation of a third phase. The organic phase isconstituted by the propane diamide of example 3 (2l -HDBDMPDA) dilutedeither in pure t-butyl benzene at a concentration of 0.75 mol.l⁻¹, or ina mixture of t-butyl benzene and decanol containing 10% decanol or 20%decanol at a concentration of 0.625 mol.l⁻¹.

The praseodymium nitrate is introduced into this organic phase until athird phase appears and the limit concentration corresponding to theappearance of said third phase is plotted. The results obtained aregiven in the attached table.

These results show that the presence of decanol is favourable, becauseit delays the appearance of the third phase and makes it possible toapproach the saturation of the solvent.

EXAMPLE 14

This example illustrates the recovery of americium and europiumrespectively present at concentrations of 10⁻⁴ mol.l for Am(III) and10⁻² mol.l⁻¹ and Eu(III) in nitric aqueous solutions of differentacidities, by means of the propane diamide constituted by compound 5(DIAM 802) of table 1.

In all cases use is made of an organic phase constituted by propanediamide DIAM 802 of the table 1 at a concentration of 0.5 mol.l⁻¹ int-butyl benzene. Extraction takes place under the same conditions as inexample 8 and after contacting for four minutes, the americium europiumconcentrations of the aqueous and organic phase are measured. Theamericium and europium distribution coefficients are then determined.

The results obtained are given in FIG. 6, where curves 15 and 16respectively illustrate the variations of D_(Am) and D_(Eu) as afunction of the nitric acid concentration of the aqueous phase (inmol.l⁻¹).

The dotted line curves 17 and 18 illustrate the results obtained withrespect to the distribution coefficient of americium (curve 17) and thedistribution coefficient of europium (curve 18), when extraction iscarried out under the same conditions using the prior artN,N'-dimethyl-N,N'-dioctyl-propane diamide.

These results show that the americium and europium distributioncoefficients are higher with the propane diamide according to theinvention.

EXAMPLE 15

This example illustrates the recovery of americium and europiumrespectively present at concentrations of 10⁻⁴ mol.l⁻¹ for Am(III) and10⁻² mol.l⁻¹ for Eu(III) in nitric aqueous solutions of differentacidities by means of the propane diamide constituted by compound 11 oftable 2 of formula: ##STR31## hereinafter referred to as 2-(3,6-OD)DBDMPDA.

In all cases, use is made of an organic phase constituted by (2-(3,6,OD)DBMPDA at a concentration of 0.5 mol.l⁻¹ in t-butyl benzene. Extractiontakes place under the same conditions as those of example 8 and after 4minutes contacting, the americium and europium concentrations of theaqueous and organic phases are measured. The americium and europiumdistribution coefficients are then determined.

The results obtained are given in FIG. 7, wherein curves 19 and 20respectively illustrate the variations of D_(Am) and D_(Eu) as afunction of the nitric acid concentration of the aqueous phase (inmol.l⁻¹) and the dotted line curve 21 illustrates the variations ofD_(Am) as a function of the nitric acid concentration of the aqueousphase, when using the prior art propane diamide (DODMPDA) instead ofcompound 11 under the same conditions.

Under the same extraction conditions, use was also made of compounds 14and 15 of table 2 and identical results were obtained.

EXAMPLE 16

This example illustrates the use of dipropane diamide constituted bycompound 13 of example 7 for the extraction of americium (III) andeuropium (III). In this example, use is made of a 4N nitric acidsolution containing americium and europium and an organic phaseconstituted by compound 13 at a concentration of 0.5 mol.l⁻¹ in t-butylbenzene.

Extraction takes place under the same conditions as those of example 8and after 4 minutes contacting, measurement takes place of the europiumconcentration of the organic and aqueous phases. Thus, the distributioncoefficient of europium D_(Eu) is determined and is equal to 2.3. Thus,compound 33 also gives good results for the recovery of europium.

EXAMPLE 17

This example illustrates the use of compound 11 of table 2 for theextraction of different metals such as U(VI), Pu(IV), Ar(IV), Fe(III)and Nb(V), from nitric solution containing 10⁻² mol.l⁻¹ of said metals.

Extraction takes place using aqueous phases of different acidities andan organic phase constituted by compound 11 of table 2 of example 6 at aconcentration of 0.5 mol.l⁻¹ in t-butyl benzene.

Extraction takes place under the same conditions as those of example 8and after 4 minutes contacting, measurement takes place of the metalconcentrations of the aqueous and organic phases. The distributioncoefficients of the different metals are then determined.

The results obtained are given in FIG. 8, where curves 22, 23, 24, 25and 26 respectively illustrate the variations of D_(U), D_(Pu), D_(Zr),D_(Fe) and D_(Nb) as a function of the nitric acid concentration of theaqueous phase (in mol.l⁻¹).

It is clear that this propane diamide is suitable for the extraction ofthe different metals and that by choosing an appropriate acidity, itmakes it possible to separate zirconium from niobium under goodconditions.

On starting with an aqueous acid solution of Sr²⁺ and carrying outextraction using the same organic phase and the same conditions ashereinbefore, a distribution coefficient D_(Sr) is obtained forstrontium, which is below 10⁻³.

                                      TABLE                                       __________________________________________________________________________                          Appearance of the                                                                      % Saturation                                   Extractant   Diluant  third phase                                                                            of the solvent                                 __________________________________________________________________________    0.75 M 2-hexyl N,N'--                                                                      t-butylbenzene                                                                         0.075 M Pr(NO.sub.3).sub.3                                                             20%                                            dibutyldimethylpropane                                                        diamide (2-HDBDMPDA)                                                          0.625 M 2-HDBDMPDA                                                                         t-butylbenzene +                                                                       0.17 M Pr(NO.sub.3).sub.3                                                              50%                                                         10% decanol                                                      0.625 M 2-HDBDMPDA                                                                         t-butylbenzene +                                                                       0.218 M Pr(NO.sub.3).sub.3                                                             70%                                                         20% decanol                                                      __________________________________________________________________________

What is claimed is:
 1. An extracting agent comprising a diluent and diamide of formula: ##STR32## in which R¹ and R², which can be the same or different, represent a straight or branched alkyl radical with 1 to 15 carbon atoms or a radical of formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m --O--R.sup.4

in which R⁴ is an alkyl radical with 1 to 6 carbon atoms, n is equal to 0 or is an integer ranging between 1 and 6, Z is a single bond or an oxygen atom and m is an integer ranging from 1 to 6, provided that Z is a single bond when n is equal to 0 and R³ represents a hydrogen atom, an alkyl radical with 1 to 15 carbon atoms, a radical of formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m --O--R.sup.4

in which n, m, Z and R⁴ have the meanings given hereinbefore, or a radical of formula: ##STR33## in which R¹ and R² have the meanings given hereinbefore, provided that R³ does not represent a hydrogen atom when R¹ and R² both represent an alkyl radical.
 2. An extracting agent according to claim 1, wherein R¹ is the methyl radical.
 3. An extracting agent according to claims 1 or 2, wherein at least one of the radicals R² and R³ is in accordance with the formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m --O--R.sup.4

in which n, m, Z and R⁴ have the meanings given in claim
 1. 4. An extracting agent according to claim 2, wherein R² is an alkyl radical and R³ the radical of formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m --O--R.sup.4

in which n, m, Z and R⁴ have the meanings given in claim
 1. 5. An extracting agent according to claim 3, wherein n is equal to 0, Z is a single bond, m is equal to 1, 2 or 3 and R⁴ is an alkyl radical with 2 to 6 carbon atoms.
 6. An extracting agent according to claim 3, wherein n is equal to 2, Z represents an oxygen atom, m is equal to 2 and R⁴ is an alkyl radical with 2 to 6 carbon atoms.
 7. An extracting agent according to claim 1, wherein R¹ is the methyl radical, R² the butyl radical and R³ the hexyl radical.
 8. An extracting agent according to claim 1, wherein R¹ is the methyl radical, R² is the butyl radical and R³ is the radical --C₂ H₄ --O--C₂ H₅.
 9. A diamide of formula: ##STR34## in which R¹ and R², which can be the same or different, represent a straight or branched alkyl radical having 1 to 15 carbon atoms or a radical of formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m --O--R.sup.4

in which R⁴ is an alkyl radical with 1 to 6 carbon atoms, n is equal to 0 or is an integer ranging between 1 and 6, Z is a single bond or an oxygen atom and m is an integer ranging between 1 and 6, provided that Z is a single bond when n is equal to 0 and R³ represents a hydrogen atom, an alkyl radical with 1 to 15 carbon atoms or a radical of formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m --O--R.sup.4

in which n, m, Z and R⁴ have the meanings given hereinbefore, provided that R³ does not represent a hydrogen atom or an alkyl radical having 1 to 3 carbon atoms when R¹ and R² both represent an alkyl radical.
 10. A diamide according to claim 9, wherein at least one of the radicals R¹, R² and R³ is in accordance with the formula:

    --(CH.sub.2).sub.n --Z--(CH.sub.2).sub.m OR.sup.4

in which n, m, Z and R⁴ have the meanings given in claim
 1. 11. A diamide according to claim 10, wherein R¹ is the methyl radical, R² is the octoxyethyl radical and R³ is a hydrogen atom.
 12. A diamide according to claim 10, wherein R¹ is the methyl radical, R² is the butyl radical and R³ is a radical chosen from among the ethyoxyethyl, butoxyethyl, hexoxyethyl and hexoxyethoxyethyl radicals.
 13. A diamide according to claim 10, wherein R¹ is the methyl radical, R² is the octyl radical and R³ is the hexoxyethyl radical.
 14. A diamide according to claim 9, wherein R¹ is the methyl radical, R² is the butyl radical and R³ is the butyl or hexyl radical. 